X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=utcp.c;h=f94c6e7e1be55ddef85b20efaff91ba143d9a620;hb=refs%2Fheads%2Ffeature%2Fefficent-buffers;hp=b939dc8a0e5e4f6723ea2eaa6f1b610adc1ecfee;hpb=850542e9585f716985c25d5995ba5bcb2cc6ba87;p=utcp

diff --git a/utcp.c b/utcp.c
index b939dc8..f94c6e7 100644
--- a/utcp.c
+++ b/utcp.c
@@ -153,12 +153,40 @@ static int32_t seqdiff(uint32_t a, uint32_t b) {
 }
 
 // Buffer functions
-// TODO: convert to ringbuffers to avoid memmove() operations.
+static bool buffer_wraps(struct buffer *buf) {
+	return buf->size - buf->offset < buf->used;
+}
+
+static bool buffer_resize(struct buffer *buf, uint32_t newsize) {
+	char *newdata = realloc(buf->data, newsize);
+
+	if(!newdata) {
+		return false;
+	}
+
+	buf->data = newdata;
+
+	if(buffer_wraps(buf)) {
+		// Shift the right part of the buffer until it hits the end of the new buffer.
+		// Old situation:
+		// [345......012]
+		// New situation:
+		// [345.........|........012]
+		uint32_t tailsize = buf->size - buf->offset;
+		uint32_t newoffset = newsize - tailsize;
+		memmove(buf + newoffset, buf + buf->offset, tailsize);
+		buf->offset = newoffset;
+	}
+
+	buf->size = newsize;
+	return true;
+}
 
 // Store data into the buffer
 static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data, size_t len) {
 	debug("buffer_put_at %lu %lu %lu\n", (unsigned long)buf->used, (unsigned long)offset, (unsigned long)len);
 
+	// Ensure we don't store more than maxsize bytes in total
 	size_t required = offset + len;
 
 	if(required > buf->maxsize) {
@@ -170,32 +198,41 @@ static ssize_t buffer_put_at(struct buffer *buf, size_t offset, const void *data
 		required = buf->maxsize;
 	}
 
+	// Check if we need to resize the buffer
 	if(required > buf->size) {
 		size_t newsize = buf->size;
 
 		if(!newsize) {
-			newsize = required;
-		} else {
-			do {
-				newsize *= 2;
-			} while(newsize < required);
+			newsize = 4096;
 		}
 
+		do {
+			newsize *= 2;
+		} while(newsize < required);
+
 		if(newsize > buf->maxsize) {
 			newsize = buf->maxsize;
 		}
 
-		char *newdata = realloc(buf->data, newsize);
-
-		if(!newdata) {
+		if(!buffer_resize(buf, newsize)) {
 			return -1;
 		}
+	}
 
-		buf->data = newdata;
-		buf->size = newsize;
+	uint32_t realoffset = buf->offset + offset;
+
+	if(buf->size - buf->offset < offset) {
+		// The offset wrapped
+		realoffset -= buf->size;
 	}
 
-	memcpy(buf->data + offset, data, len);
+	if(buf->size - realoffset < len) {
+		// The new chunk of data must be wrapped
+		memcpy(buf->data + realoffset, data, buf->size - realoffset);
+		memcpy(buf->data, (char *)data + buf->size - realoffset, len - (buf->size - realoffset));
+	} else {
+		memcpy(buf->data + realoffset, data, len);
+	}
 
 	if(required > buf->used) {
 		buf->used = required;
@@ -208,52 +245,72 @@ static ssize_t buffer_put(struct buffer *buf, const void *data, size_t len) {
 	return buffer_put_at(buf, buf->used, data, len);
 }
 
-// Get data from the buffer. data can be NULL.
-static ssize_t buffer_get(struct buffer *buf, void *data, size_t len) {
-	if(len > buf->used) {
-		len = buf->used;
+// Copy data from the buffer without removing it.
+static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
+	// Ensure we don't copy more than is actually stored in the buffer
+	if(offset >= buf->used) {
+		return 0;
 	}
 
-	if(data) {
-		memcpy(data, buf->data, len);
+	if(buf->used - offset < len) {
+		len = buf->used - offset;
 	}
 
-	if(len < buf->used) {
-		memmove(buf->data, buf->data + len, buf->used - len);
+	uint32_t realoffset = buf->offset + offset;
+
+	if(buf->size - buf->offset < offset) {
+		// The offset wrapped
+		realoffset -= buf->size;
+	}
+
+	if(buf->size - realoffset < len) {
+		// The data is wrapped
+		memcpy(data, buf->data + realoffset, buf->size - realoffset);
+		memcpy((char *)data + buf->size - realoffset, buf->data, len - (buf->size - realoffset));
+	} else {
+		memcpy(data, buf->data + realoffset, len);
 	}
 
-	buf->used -= len;
 	return len;
 }
 
-// Copy data from the buffer without removing it.
-static ssize_t buffer_copy(struct buffer *buf, void *data, size_t offset, size_t len) {
-	if(offset >= buf->used) {
-		return 0;
-	}
+// Get data from the buffer.
+static ssize_t buffer_get(struct buffer *buf, void *data, size_t len) {
+	len = buffer_copy(buf, data, 0, len);
 
-	if(offset + len > buf->used) {
-		len = buf->used - offset;
+	if(buf->size - buf->offset < len) {
+		buf->offset -= buf->size;
 	}
 
-	memcpy(data, buf->data + offset, len);
+	buf->offset += len;
+	buf->used -= len;
 	return len;
 }
 
-static bool buffer_init(struct buffer *buf, uint32_t len, uint32_t maxlen) {
-	memset(buf, 0, sizeof(*buf));
+// Discard data from the buffer.
+static ssize_t buffer_discard(struct buffer *buf, size_t len) {
+	if(buf->used < len) {
+		len = buf->used;
+	}
 
-	if(len) {
-		buf->data = malloc(len);
+	if(buf->size - buf->offset < len) {
+		buf->offset -= buf->size;
+	}
 
-		if(!buf->data) {
-			return false;
-		}
+	buf->offset += len;
+	buf->used -= len;
+
+	return len;
+}
+
+static bool buffer_set_size(struct buffer *buf, uint32_t minsize, uint32_t maxsize) {
+	if(maxsize < minsize) {
+		maxsize = minsize;
 	}
 
-	buf->size = len;
-	buf->maxsize = maxlen;
-	return true;
+	buf->maxsize = maxsize;
+
+	return buf->size >= minsize || buffer_resize(buf, minsize);
 }
 
 static void buffer_exit(struct buffer *buf) {
@@ -360,12 +417,12 @@ static struct utcp_connection *allocate_connection(struct utcp *utcp, uint16_t s
 		return NULL;
 	}
 
-	if(!buffer_init(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
+	if(!buffer_set_size(&c->sndbuf, DEFAULT_SNDBUFSIZE, DEFAULT_MAXSNDBUFSIZE)) {
 		free(c);
 		return NULL;
 	}
 
-	if(!buffer_init(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
+	if(!buffer_set_size(&c->rcvbuf, DEFAULT_RCVBUFSIZE, DEFAULT_MAXRCVBUFSIZE)) {
 		buffer_exit(&c->sndbuf);
 		free(c);
 		return NULL;
@@ -415,13 +472,13 @@ static void update_rtt(struct utcp_connection *c, uint32_t rtt) {
 	if(!utcp->srtt) {
 		utcp->srtt = rtt;
 		utcp->rttvar = rtt / 2;
-		utcp->rto = rtt + max(2 * rtt, CLOCK_GRANULARITY);
 	} else {
 		utcp->rttvar = (utcp->rttvar * 3 + absdiff(utcp->srtt, rtt)) / 4;
 		utcp->srtt = (utcp->srtt * 7 + rtt) / 8;
-		utcp->rto = utcp->srtt + max(utcp->rttvar, CLOCK_GRANULARITY);
 	}
 
+	utcp->rto = utcp->srtt + max(4 * utcp->rttvar, CLOCK_GRANULARITY);
+
 	if(utcp->rto > MAX_RTO) {
 		utcp->rto = MAX_RTO;
 	}
@@ -453,7 +510,7 @@ struct utcp_connection *utcp_connect_ex(struct utcp *utcp, uint16_t dst, utcp_re
 		return NULL;
 	}
 
-	assert((flags & ~0xf) == 0);
+	assert((flags & ~0x1f) == 0);
 
 	c->flags = flags;
 	c->recv = recv;
@@ -527,13 +584,7 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 	struct {
 		struct hdr hdr;
 		uint8_t data[];
-	} *pkt;
-
-	pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-	if(!pkt) {
-		return;
-	}
+	} *pkt = c->utcp->pkt;
 
 	pkt->hdr.src = c->src;
 	pkt->hdr.dst = c->dst;
@@ -566,8 +617,6 @@ static void ack(struct utcp_connection *c, bool sendatleastone) {
 		print_packet(c->utcp, "send", pkt, sizeof(pkt->hdr) + seglen);
 		c->utcp->send(c->utcp, pkt, sizeof(pkt->hdr) + seglen);
 	} while(left);
-
-	free(pkt);
 }
 
 ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
@@ -580,12 +629,12 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
 	switch(c->state) {
 	case CLOSED:
 	case LISTEN:
-	case SYN_SENT:
-	case SYN_RECEIVED:
 		debug("Error: send() called on unconnected connection %p\n", c);
 		errno = ENOTCONN;
 		return -1;
 
+	case SYN_SENT:
+	case SYN_RECEIVED:
 	case ESTABLISHED:
 	case CLOSE_WAIT:
 		break;
@@ -611,16 +660,45 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
 		return -1;
 	}
 
+	// Check if we need to be able to buffer all data
+
+	if(c->flags & UTCP_NO_PARTIAL) {
+		if(len > buffer_free(&c->sndbuf)) {
+			if(len > c->sndbuf.maxsize) {
+				errno = EMSGSIZE;
+				return -1;
+			} else {
+				errno = EWOULDBLOCK;
+				return 0;
+			}
+		}
+	}
+
 	// Add data to send buffer.
 
-	len = buffer_put(&c->sndbuf, data, len);
+	if(is_reliable(c) || (c->state != SYN_SENT && c->state != SYN_RECEIVED)) {
+		len = buffer_put(&c->sndbuf, data, len);
+	} else {
+		return 0;
+	}
 
 	if(len <= 0) {
-		errno = EWOULDBLOCK;
-		return 0;
+		if(is_reliable(c)) {
+			errno = EWOULDBLOCK;
+			return 0;
+		} else {
+			return len;
+		}
 	}
 
 	c->snd.last += len;
+
+	// Don't send anything yet if the connection has not fully established yet
+
+	if(c->state == SYN_SENT || c->state == SYN_RECEIVED) {
+		return len;
+	}
+
 	ack(c, false);
 
 	if(!is_reliable(c)) {
@@ -632,6 +710,11 @@ ssize_t utcp_send(struct utcp_connection *c, const void *data, size_t len) {
 		start_retransmit_timer(c);
 	}
 
+	if(is_reliable(c) && !timerisset(&c->conn_timeout)) {
+		gettimeofday(&c->conn_timeout, NULL);
+		c->conn_timeout.tv_sec += c->utcp->timeout;
+	}
+
 	return len;
 }
 
@@ -653,13 +736,7 @@ static void retransmit(struct utcp_connection *c) {
 	struct {
 		struct hdr hdr;
 		uint8_t data[];
-	} *pkt;
-
-	pkt = malloc(sizeof(pkt->hdr) + c->utcp->mtu);
-
-	if(!pkt) {
-		return;
-	}
+	} *pkt = c->utcp->pkt;
 
 	pkt->hdr.src = c->src;
 	pkt->hdr.dst = c->dst;
@@ -739,7 +816,7 @@ static void retransmit(struct utcp_connection *c) {
 	c->rtt_start.tv_sec = 0; // invalidate RTT timer
 
 cleanup:
-	free(pkt);
+	return;
 }
 
 /* Update receive buffer and SACK entries after consuming data.
@@ -892,6 +969,8 @@ static void handle_incoming_data(struct utcp_connection *c, uint32_t seq, const
 
 
 ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
+	const uint8_t *ptr = data;
+
 	if(!utcp) {
 		errno = EFAULT;
 		return -1;
@@ -919,8 +998,8 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
 	// Make a copy from the potentially unaligned data to a struct hdr
 
-	memcpy(&hdr, data, sizeof(hdr));
-	data += sizeof(hdr);
+	memcpy(&hdr, ptr, sizeof(hdr));
+	ptr += sizeof(hdr);
 	len -= sizeof(hdr);
 
 	// Drop packets with an unknown CTL flag
@@ -952,7 +1031,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 				return -1;
 			}
 
-			init = data;
+			init = ptr;
 			break;
 
 		default:
@@ -961,7 +1040,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		}
 
 		len -= auxlen;
-		data += auxlen;
+		ptr += auxlen;
 
 		if(!(aux & 0x800)) {
 			break;
@@ -972,11 +1051,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 			return -1;
 		}
 
-		memcpy(&aux, data, 2);
+		memcpy(&aux, ptr, 2);
 		len -= 2;
-		data += 2;
+		ptr += 2;
 	}
 
+	bool has_data = len || (hdr.ctl & (SYN | FIN));
+
 	// Try to match the packet to an existing connection
 
 	struct utcp_connection *c = find_connection(utcp, hdr.dst, hdr.src);
@@ -1019,6 +1100,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 				c->flags = UTCP_TCP;
 			}
 
+synack:
 			// Return SYN+ACK, go to SYN_RECEIVED state
 			c->snd.wnd = hdr.wnd;
 			c->rcv.irs = hdr.seq;
@@ -1071,8 +1153,6 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
 	// It is for an existing connection.
 
-	uint32_t prevrcvnxt = c->rcv.nxt;
-
 	// 1. Drop invalid packets.
 
 	// 1a. Drop packets that should not happen in our current state.
@@ -1096,41 +1176,43 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		break;
 	}
 
-	// 1b. Drop packets with a sequence number not in our receive window.
+	// 1b. Discard data that is not in our receive window.
 
-	bool acceptable;
+	if(is_reliable(c)) {
+		bool acceptable;
 
-	if(c->state == SYN_SENT) {
-		acceptable = true;
-	} else if(len == 0) {
-		acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
-	} else {
-		int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
+		if(c->state == SYN_SENT) {
+			acceptable = true;
+		} else if(len == 0) {
+			acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0;
+		} else {
+			int32_t rcv_offset = seqdiff(hdr.seq, c->rcv.nxt);
 
-		// cut already accepted front overlapping
-		if(rcv_offset < 0) {
-			acceptable = len > (size_t) - rcv_offset;
+			// cut already accepted front overlapping
+			if(rcv_offset < 0) {
+				acceptable = len > (size_t) - rcv_offset;
 
-			if(acceptable) {
-				data -= rcv_offset;
-				len += rcv_offset;
-				hdr.seq -= rcv_offset;
+				if(acceptable) {
+					ptr -= rcv_offset;
+					len += rcv_offset;
+					hdr.seq -= rcv_offset;
+				}
+			} else {
+				acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
 			}
-		} else {
-			acceptable = seqdiff(hdr.seq, c->rcv.nxt) >= 0 && seqdiff(hdr.seq, c->rcv.nxt) + len <= c->rcvbuf.maxsize;
 		}
-	}
 
-	if(!acceptable) {
-		debug("Packet not acceptable, %u <= %u + %lu < %u\n", c->rcv.nxt, hdr.seq, (unsigned long)len, c->rcv.nxt + c->rcvbuf.maxsize);
+		if(!acceptable) {
+			debug("Packet not acceptable, %u <= %u + %lu < %u\n", c->rcv.nxt, hdr.seq, (unsigned long)len, c->rcv.nxt + c->rcvbuf.maxsize);
 
-		// Ignore unacceptable RST packets.
-		if(hdr.ctl & RST) {
-			return 0;
-		}
+			// Ignore unacceptable RST packets.
+			if(hdr.ctl & RST) {
+				return 0;
+			}
 
-		// Otherwise, continue processing.
-		len = 0;
+			// Otherwise, continue processing.
+			len = 0;
+		}
 	}
 
 	c->snd.wnd = hdr.wnd; // TODO: move below
@@ -1139,6 +1221,12 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	// ackno should not roll back, and it should also not be bigger than what we ever could have sent
 	// (= snd.una + c->sndbuf.used).
 
+	if(!is_reliable(c)) {
+		if(hdr.ack != c->snd.last && c->state >= ESTABLISHED) {
+			hdr.ack = c->snd.una;
+		}
+	}
+
 	if(hdr.ctl & ACK && (seqdiff(hdr.ack, c->snd.last) > 0 || seqdiff(hdr.ack, c->snd.una) < 0)) {
 		debug("Packet ack seqno out of range, %u <= %u < %u\n", c->snd.una, hdr.ack, c->snd.una + c->sndbuf.used);
 
@@ -1167,6 +1255,10 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 				c->recv(c, NULL, 0);
 			}
 
+			if(c->poll && !c->reapable) {
+				c->poll(c, 0);
+			}
+
 			return 0;
 
 		case SYN_RECEIVED:
@@ -1194,6 +1286,10 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 				c->recv(c, NULL, 0);
 			}
 
+			if(c->poll && !c->reapable) {
+				c->poll(c, 0);
+			}
+
 			return 0;
 
 		case CLOSING:
@@ -1222,14 +1318,16 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		}
 	}
 
+	uint32_t advanced;
+
 	if(!(hdr.ctl & ACK)) {
+		advanced = 0;
 		goto skip_ack;
 	}
 
 	// 3. Advance snd.una
 
-	uint32_t advanced = seqdiff(hdr.ack, c->snd.una);
-	prevrcvnxt = c->rcv.nxt;
+	advanced = seqdiff(hdr.ack, c->snd.una);
 
 	if(advanced) {
 		// RTT measurement
@@ -1261,11 +1359,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 
 		assert(data_acked >= 0);
 
+#ifndef NDEBUG
 		int32_t bufused = seqdiff(c->snd.last, c->snd.una);
 		assert(data_acked <= bufused);
+#endif
 
 		if(data_acked) {
-			buffer_get(&c->sndbuf, NULL, data_acked);
+			buffer_discard(&c->sndbuf, data_acked);
 		}
 
 		// Also advance snd.nxt if possible
@@ -1294,7 +1394,7 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 		case CLOSING:
 			if(c->snd.una == c->snd.last) {
 				gettimeofday(&c->conn_timeout, NULL);
-				c->conn_timeout.tv_sec += 60;
+				c->conn_timeout.tv_sec += utcp->timeout;
 				set_state(c, TIME_WAIT);
 			}
 
@@ -1322,12 +1422,13 @@ ssize_t utcp_recv(struct utcp *utcp, const void *data, size_t len) {
 	// 4. Update timers
 
 	if(advanced) {
-		timerclear(&c->conn_timeout); // It will be set anew in utcp_timeout() if c->snd.una != c->snd.nxt.
-
 		if(c->snd.una == c->snd.last) {
 			stop_retransmit_timer(c);
+			timerclear(&c->conn_timeout);
 		} else if(is_reliable(c)) {
 			start_retransmit_timer(c);
+			gettimeofday(&c->conn_timeout, NULL);
+			c->conn_timeout.tv_sec += utcp->timeout;
 		}
 	}
 
@@ -1345,11 +1446,21 @@ skip_ack:
 
 			c->rcv.irs = hdr.seq;
 			c->rcv.nxt = hdr.seq;
-			set_state(c, ESTABLISHED);
+
+			if(c->shut_wr) {
+				c->snd.last++;
+				set_state(c, FIN_WAIT_1);
+			} else {
+				set_state(c, ESTABLISHED);
+			}
+
 			// TODO: notify application of this somehow.
 			break;
 
 		case SYN_RECEIVED:
+			// This is a retransmit of a SYN, send back the SYNACK.
+			goto synack;
+
 		case ESTABLISHED:
 		case FIN_WAIT_1:
 		case FIN_WAIT_2:
@@ -1420,12 +1531,12 @@ skip_ack:
 			return 0;
 		}
 
-		handle_incoming_data(c, hdr.seq, data, len);
+		handle_incoming_data(c, hdr.seq, ptr, len);
 	}
 
 	// 7. Process FIN stuff
 
-	if((hdr.ctl & FIN) && hdr.seq + len == c->rcv.nxt) {
+	if((hdr.ctl & FIN) && (!is_reliable(c) || hdr.seq + len == c->rcv.nxt)) {
 		switch(c->state) {
 		case SYN_SENT:
 		case SYN_RECEIVED:
@@ -1445,7 +1556,7 @@ skip_ack:
 
 		case FIN_WAIT_2:
 			gettimeofday(&c->conn_timeout, NULL);
-			c->conn_timeout.tv_sec += 60;
+			c->conn_timeout.tv_sec += utcp->timeout;
 			set_state(c, TIME_WAIT);
 			break;
 
@@ -1467,7 +1578,7 @@ skip_ack:
 		c->rcv.nxt++;
 		len++;
 
-		// Inform the application that the peer closed the connection.
+		// Inform the application that the peer closed its end of the connection.
 		if(c->recv) {
 			errno = 0;
 			c->recv(c, NULL, 0);
@@ -1475,12 +1586,15 @@ skip_ack:
 	}
 
 	// Now we send something back if:
-	// - we advanced rcv.nxt (ie, we got some data that needs to be ACKed)
+	// - we received data, so we have to send back an ACK
 	//   -> sendatleastone = true
 	// - or we got an ack, so we should maybe send a bit more data
 	//   -> sendatleastone = false
 
-	ack(c, len || prevrcvnxt != c->rcv.nxt);
+	if(is_reliable(c) || hdr.ctl & SYN || hdr.ctl & FIN) {
+		ack(c, has_data);
+	}
+
 	return 0;
 
 reset:
@@ -1533,6 +1647,13 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
 		return 0;
 	}
 
+	// Only process shutting down writes once.
+	if(c->shut_wr) {
+		return 0;
+	}
+
+	c->shut_wr = true;
+
 	switch(c->state) {
 	case CLOSED:
 	case LISTEN:
@@ -1540,7 +1661,6 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
 		return -1;
 
 	case SYN_SENT:
-		set_state(c, CLOSED);
 		return 0;
 
 	case SYN_RECEIVED:
@@ -1573,36 +1693,24 @@ int utcp_shutdown(struct utcp_connection *c, int dir) {
 	return 0;
 }
 
-int utcp_close(struct utcp_connection *c) {
-	if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN) {
-		return -1;
-	}
-
-	c->recv = NULL;
-	c->poll = NULL;
-	c->reapable = true;
-	return 0;
-}
-
-int utcp_abort(struct utcp_connection *c) {
+static bool reset_connection(struct utcp_connection *c) {
 	if(!c) {
 		errno = EFAULT;
-		return -1;
+		return false;
 	}
 
 	if(c->reapable) {
 		debug("Error: abort() called on closed connection %p\n", c);
 		errno = EBADF;
-		return -1;
+		return false;
 	}
 
 	c->recv = NULL;
 	c->poll = NULL;
-	c->reapable = true;
 
 	switch(c->state) {
 	case CLOSED:
-		return 0;
+		return true;
 
 	case LISTEN:
 	case SYN_SENT:
@@ -1610,7 +1718,7 @@ int utcp_abort(struct utcp_connection *c) {
 	case LAST_ACK:
 	case TIME_WAIT:
 		set_state(c, CLOSED);
-		return 0;
+		return true;
 
 	case SYN_RECEIVED:
 	case ESTABLISHED:
@@ -1634,6 +1742,59 @@ int utcp_abort(struct utcp_connection *c) {
 
 	print_packet(c->utcp, "send", &hdr, sizeof(hdr));
 	c->utcp->send(c->utcp, &hdr, sizeof(hdr));
+	return true;
+}
+
+// Closes all the opened connections
+void utcp_abort_all_connections(struct utcp *utcp) {
+	if(!utcp) {
+		errno = EINVAL;
+		return;
+	}
+
+	for(int i = 0; i < utcp->nconnections; i++) {
+		struct utcp_connection *c = utcp->connections[i];
+
+		if(c->reapable || c->state == CLOSED) {
+			continue;
+		}
+
+		utcp_recv_t old_recv = c->recv;
+		utcp_poll_t old_poll = c->poll;
+
+		reset_connection(c);
+
+		if(old_recv) {
+			errno = 0;
+			old_recv(c, NULL, 0);
+		}
+
+		if(old_poll && !c->reapable) {
+			errno = 0;
+			old_poll(c, 0);
+		}
+	}
+
+	return;
+}
+
+int utcp_close(struct utcp_connection *c) {
+	if(utcp_shutdown(c, SHUT_RDWR) && errno != ENOTCONN) {
+		return -1;
+	}
+
+	c->recv = NULL;
+	c->poll = NULL;
+	c->reapable = true;
+	return 0;
+}
+
+int utcp_abort(struct utcp_connection *c) {
+	if(!reset_connection(c)) {
+		return -1;
+	}
+
+	c->reapable = true;
 	return 0;
 }
 
@@ -1674,6 +1835,10 @@ struct timeval utcp_timeout(struct utcp *utcp) {
 				c->recv(c, NULL, 0);
 			}
 
+			if(c->poll && !c->reapable) {
+				c->poll(c, 0);
+			}
+
 			continue;
 		}
 
@@ -1739,7 +1904,7 @@ struct utcp *utcp_init(utcp_accept_t accept, utcp_pre_accept_t pre_accept, utcp_
 	utcp->pre_accept = pre_accept;
 	utcp->send = send;
 	utcp->priv = priv;
-	utcp->mtu = DEFAULT_MTU;
+	utcp_set_mtu(utcp, DEFAULT_MTU);
 	utcp->timeout = DEFAULT_USER_TIMEOUT; // sec
 	utcp->rto = START_RTO; // usec
 
@@ -1754,11 +1919,16 @@ void utcp_exit(struct utcp *utcp) {
 	for(int i = 0; i < utcp->nconnections; i++) {
 		struct utcp_connection *c = utcp->connections[i];
 
-		if(!c->reapable)
+		if(!c->reapable) {
 			if(c->recv) {
 				c->recv(c, NULL, 0);
 			}
 
+			if(c->poll && !c->reapable) {
+				c->poll(c, 0);
+			}
+		}
+
 		buffer_exit(&c->rcvbuf);
 		buffer_exit(&c->sndbuf);
 		free(c);
@@ -1773,10 +1943,25 @@ uint16_t utcp_get_mtu(struct utcp *utcp) {
 }
 
 void utcp_set_mtu(struct utcp *utcp, uint16_t mtu) {
-	// TODO: handle overhead of the header
-	if(utcp) {
-		utcp->mtu = mtu;
+	if(!utcp) {
+		return;
+	}
+
+	if(mtu <= sizeof(struct hdr)) {
+		return;
 	}
+
+	if(mtu > utcp->mtu) {
+		char *new = realloc(utcp->pkt, mtu + sizeof(struct hdr));
+
+		if(!new) {
+			return;
+		}
+
+		utcp->pkt = new;
+	}
+
+	utcp->mtu = mtu;
 }
 
 void utcp_reset_timers(struct utcp *utcp) {
@@ -1793,9 +1978,21 @@ void utcp_reset_timers(struct utcp *utcp) {
 	then.tv_sec += utcp->timeout;
 
 	for(int i = 0; i < utcp->nconnections; i++) {
-		utcp->connections[i]->rtrx_timeout = now;
-		utcp->connections[i]->conn_timeout = then;
-		utcp->connections[i]->rtt_start.tv_sec = 0;
+		struct utcp_connection *c = utcp->connections[i];
+
+		if(c->reapable) {
+			continue;
+		}
+
+		if(timerisset(&c->rtrx_timeout)) {
+			c->rtrx_timeout = now;
+		}
+
+		if(timerisset(&c->conn_timeout)) {
+			c->conn_timeout = then;
+		}
+
+		c->rtt_start.tv_sec = 0;
 	}
 
 	if(utcp->rto > START_RTO) {
@@ -1818,9 +2015,18 @@ size_t utcp_get_sndbuf(struct utcp_connection *c) {
 }
 
 size_t utcp_get_sndbuf_free(struct utcp_connection *c) {
-	if(c && (c->state == ESTABLISHED || c->state == CLOSE_WAIT)) {
+	if(!c) {
+		return 0;
+	}
+
+	switch(c->state) {
+	case SYN_SENT:
+	case SYN_RECEIVED:
+	case ESTABLISHED:
+	case CLOSE_WAIT:
 		return buffer_free(&c->sndbuf);
-	} else {
+
+	default:
 		return 0;
 	}
 }
@@ -1861,6 +2067,14 @@ void utcp_set_rcvbuf(struct utcp_connection *c, size_t size) {
 	}
 }
 
+size_t utcp_get_sendq(struct utcp_connection *c) {
+	return c->sndbuf.used;
+}
+
+size_t utcp_get_recvq(struct utcp_connection *c) {
+	return c->rcvbuf.used;
+}
+
 bool utcp_get_nodelay(struct utcp_connection *c) {
 	return c ? c->nodelay : false;
 }
@@ -1903,3 +2117,53 @@ void utcp_set_accept_cb(struct utcp *utcp, utcp_accept_t accept, utcp_pre_accept
 		utcp->pre_accept = pre_accept;
 	}
 }
+
+void utcp_expect_data(struct utcp_connection *c, bool expect) {
+	if(!c || c->reapable) {
+		return;
+	}
+
+	if(!(c->state == ESTABLISHED || c->state == FIN_WAIT_1 || c->state == FIN_WAIT_2)) {
+		return;
+	}
+
+	if(expect) {
+		// If we expect data, start the connection timer.
+		if(!timerisset(&c->conn_timeout)) {
+			gettimeofday(&c->conn_timeout, NULL);
+			c->conn_timeout.tv_sec += c->utcp->timeout;
+		}
+	} else {
+		// If we want to cancel expecting data, only clear the timer when there is no unACKed data.
+		if(c->snd.una == c->snd.last) {
+			timerclear(&c->conn_timeout);
+		}
+	}
+}
+
+void utcp_offline(struct utcp *utcp, bool offline) {
+	struct timeval now;
+	gettimeofday(&now, NULL);
+
+	for(int i = 0; i < utcp->nconnections; i++) {
+		struct utcp_connection *c = utcp->connections[i];
+
+		if(c->reapable) {
+			continue;
+		}
+
+		utcp_expect_data(c, offline);
+
+		if(!offline) {
+			if(timerisset(&c->rtrx_timeout)) {
+				c->rtrx_timeout = now;
+			}
+
+			utcp->connections[i]->rtt_start.tv_sec = 0;
+		}
+	}
+
+	if(!offline && utcp->rto > START_RTO) {
+		utcp->rto = START_RTO;
+	}
+}